The decisive New Hampshire first-in-the-nation primary win for Vermont Sen. Bernie Sanders puts his platform of democratic socialism increasingly in the spotlight.

“Together we have sent a message that will echo from Wall Street to Washington, from Maine to California,” Sanders said in his Feb. 9 victory speech. “And that is that the government of our great country belongs to all of the people, and not just a handful of wealthy campaign contributors and their ‘super PACs.’”

But what does the Church say about socialism? Let’s consider the basic points.

What is socialism?

Socialism advocates for the ownership of property, not by individuals, but by society in general. But a quick and easy definition is hard because there are so many different versions of socialism.

Some socialists say there should be no private property at all, while many others aim for the socialization of only the major industries. Some say ownership of such property should be shared by everyone in society, while others say that means, in practical terms, government ownership. The differences go on and on.

Modern socialism developed initially in the late 18th century and then strongly in the late 19th, as a reaction to the brutal excesses of capitalism. Then and now, socialists have seen their approach as a more just and natural arrangement for the ownership of goods. Though socialist politics are relatively uncommon in the United States, socialism is a much more dominant force in other regions of the globe.

What does the Church have to say about socialism?

To start with, let’s be clear: the Catholic Church has condemned socialism, repeatedly and emphatically. But that condemnation has included some important nuances and qualifications.

Pope Leo XIII (1878-1903) firmly rejected socialism because of what he took to be its total rejection of private property. Indeed, this was a key principle of the Marxist socialism that was popular in Leo’s day. Catholic teaching defends the right to private property, though with strong qualifications. In his important encyclical Rerum Novarum (“On Capital and Labor”), issued in 1891, Leo said socialism calls for all possessions to “become the common property of all” and that such an arrangement “would rob the lawful possessor, distort the functions of the State, and create utter confusion in the community.”

Pope Pius XI (1922-1939) similarly rejected the materialist philosophy — that is, the complete rejection in principle of spiritual or divine realities — that he said was at the foundation of socialism. In his encyclical Quadragesimo Anno (“On reconstruction of the social order”), Pius concluded that because of this, “no one can be at the same time a sincere Catholic and a true socialist.”

More recently, Pope St. John Paul II (1978-2005) insisted that socialism sacrifices the dignity of every human person in the name of economic or national security.

“Socialism,” he said in his encyclical Centesimus Annus, “considers the individual person simply as an element, a molecule within the social organism, so that the good of the individual is completely subordinated to the functioning of the socio-economic mechanism.”

Many socialisms

To be fair, though, many socialists have insisted that the papal condemnations don’t reflect the ideas they really promote. Many socialists are open to some private property, express a strong faith in God and promote human dignity. Indeed, many — including, it’s fair to say, Bernie Sanders — embrace socialism specifically because of its strong impulse toward a just distribution of goods and services among all people, and that’s a conviction that finds serious support in Catholic doctrine. The popes have acknowledged this to some degree.

Pope Pius XI pointed out in Quadragesimo Anno that some ideas often considered central to socialism — for example, government ownership of some functions and means of production — are in fact compatible with Catholic faith. The demands of socialism, he said, “at times come very near those that Christian reformers of society justly insist upon,” but he added that Catholics can pursue these ideals without becoming socialists.

In an important apostolic letter, Octogesima Adveniens, written on the 80th anniversary of Rerum Novarum, Pope Paul VI acknowledged that not all socialist ideas are to be rejected. He suggested that for Catholics, a certain “degree of commitment” to socialism might be possible. But he strongly cautioned the faithful not to “idealize” socialism simply as a movement for justice, solidarity and equality while forgetting “the limitations of the historical socialist movements, which remain conditioned by the ideologies from which they originated.”

Could a Catholic vote for a socialist?

Asking whether a Catholic could be a true socialist is very different than asking whether he or she could vote for a socialist candidate or support a socialist serving in high political office. Indeed, the Church has clearly recognized the possibility of real collaboration by Catholics with socialists and others in order to build a better world for all people.

In the early 1900s, for example, when a controversy erupted in Germany over whether Catholics could legitimately join and support the activities of labor unions run by socialists, Pope Pius X approved of such collaboration in the name of protecting workers’ rights and improving other social conditions. Pope Paul VI devoted much space in his encyclical Populorum Progressio to the importance of collaboration among peoples and governments of various types to improve society. In Octogesima Adveniens, the same pope acknowledged that Christians might find some Marxist ideas and tools, like social analysis, useful in the work of social justice.

More generally, Catholic moral theology’s distinction between formal cooperation and material cooperation in evil suggests that a Catholic might legitimately support a socialist candidate for important reasons other than the fact that he is a socialist. Much would depend on the candidate’s positions on important issues on which he’ll likely have an impact, such as abortion, war, environmental concerns and care for the poor.

How closely Catholics will have to think through such questions in the next nine months will depend on whether or not Sanders’ campaign continues to be successful.